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Assimilation of Global Radar Backscatter and Radiometer Brightness Temperature Observations to Improve Soil Moisture and Land Evaporation EstimatesActive radar backscatter (s◦) observations from the Advanced Scatterometer (ASCAT) and passive radiometer brightness temperature (TB) observations from the Soil Moisture Ocean Salinity (SMOS) mission are assimilated either individually or jointly into the Global Land Evaporation Amsterdam Model (GLEAM) to improve its simulations of soil moisture and land evaporation. To enable s◦ and TB assimilation, GLEAM is coupled to the Water Cloud Model and the L-band Microwave Emission from the Biosphere (L-MEB) model. The innovations, i.e. differences between observations and simulations, are mapped onto the model soil moisture states through an Ensemble Kalman Filter. The validation of surface (0-10 cm) soil moisture simulations over the period 2010-2014 against in situ measurements from the International Soil Moisture Network (ISMN) shows that assimilating s◦ or TB alone improves the average correlation of seasonal anomalies (Ran) from 0.514 to 0.547 and 0.548, respectively. The joint assimilation further improves Ran to 0.559. Associated enhancements in daily evaporative flux simulations by GLEAM are validated based on measurements from 22 FLUXNET stations. Again, the singular assimilation improves Ran from 0.502 to 0.536 and 0.533, respectively for s◦ and TB, whereas the best performance is observed for the joint assimilation (Ran = 0.546). These results demonstrate the complementary value of assimilating radar backscatter observations together with brightness temperatures for improving estimates of hydrological variables, as their joint assimilation outperforms the assimilation of each observation type separately.
Document ID
20170001305
Document Type
Reprint (Version printed in journal)
Authors
Lievens, H. (Science Collaborator Greenbelt, MD, United States)
Martens, B. (Ghent Univ. Belgium)
Verhoest, N. E. C. (Ghent Univ. Belgium)
Hahn, S. (Wien Univ. Austria)
Reichle, R. H. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Miralles, D. G. (VU Univ. Amsterdam, Netherlands)
Date Acquired
February 3, 2017
Publication Date
January 1, 2017
Publication Information
Publication: Remote Sensing of Environment
Volume: 189
ISSN: 0034-4257
Subject Category
Earth Resources and Remote Sensing
Report/Patent Number
GSFC-E-DAA-TN38389
Distribution Limits
Public
Copyright
Other
Keywords
GLEAM
SMOS
ASCAT